Allen Formation

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The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.[1] Dinosaur remains are among the fossils that have been recovered from the formation.[2] Indeterminate chelid remains and other vertebrates have also been discovered in this formation.[3]

Description

File:Allen Formation Fauna.png
Fauna of Allen Formation

Uliana and Dellapé defined the formation's stratotype in 1981 in the eastern area of the Bajo de Añelo, where the relation between the base and top is clearly exposed. The deposits are mostly clastic, interbedded with banks of limestone and layers of anhydrite, which were defined as continental and shallow marine facies associated with semiarid conditions.[4]

The interpreted sedimentary paleoenvironments range from purely continental such as ephemeral lacustrine, aeolian and fluvial systems to coastal marine paleoenvironments with development of estuaries and tidal flats, followed by a lagoon sedimentary stage from marsh to sea with carbonate precipitation in an area protected from waves, ending with a retraction leading to the accumulation of evaporites.[4]

Armas and Sánchez performed a detailed facies analysis of the formation in 2015, where the authors concluded the formation represents a hybrid coastal system of tidal flats, dominated by Atlantic ingressions, with a large storm influence in some areas linked to aeolian systems.[5]

Fossil content

File:Quilmesaurus hunting Bonapartesaurus version 2.jpg
Life restoration of Dinosaurs discovered from Allen Formation

Dinosaurs

Template:Paleobiota-key-compact Dinosaur eggs are known from the formation.[6]

Ornithischians

Ankylosaurs
Genus Species Location Stratigraphic position Material Notes Images
Ankylosauria[7] Indeterminate Arriagada Farm Two teeth, five osteoderms, and a partial sacrum Fossil remains possibly belonging to a parankylosaur distinct from Patagopelta
Patagopelta P. cristata Salitral Moreno locality Lower Tooth, three posterior dorsal vertebrae, caudal vertebrae, two caudal centra, right femur, partial cervical half ring, and osteoderms. A parankylosaur[8]
File:Patagopelta into the water.png
Hadrosaurs
Genus Species Location Stratigraphic position Material Notes Images
Bonapartesaurus B. rionegrensis Salitral Moreno and Islas Malvinas. Lower A partial skeleton. A hadrosaur
File:Bonapartesaurus rionegrensis.png
Kelumapusaura K. machi Cerro Matadero, Arriagada Farm Upper Partial skull, a cervical vertebrae, several sacrals, sternal rib and sternal plate, and multiple referred specimens found in a bonebed A saurolophine hadrosaur[9]
File:Kelumapusaura.jpg
Lapampasaurus L. cholinoi Islas Malvinas Lower Elements of the axial and appendicular skeleton of a subadult individual A hadrosaur[10]
Willinakaqe W. salitralensis Salitral Moreno site. Lower A right premaxilla. A saurolophine hadrosaur[11]

Saurischians

Sauropods
Genus Species Location Stratigraphic position Material Notes Images
Aeolosaurus Indeterminate Lower A titanosaur[6]
File:Aeolosaurus-rionegrinus-JD-2020-1.png

Bonatitan

B.reigi[12]

Lower Braincases, caudal vertebrae, and several limb elements A titanosaur[12]
Menucocelsior M. arriagadai Lower Seventeen caudal vertebrae and several appendicular bones: a right humerus, a left fibula and some metapodial. A titanosaur[13]
Panamericansaurus P. schroederi "Five tail vertebrata, sacral vertebrae, left humerus and rib fragments" A titanosaur[6][14]
Pellegrinisaurus? P. powelli Lower (if it is from the formation) "Dorsal and caudal vertebrae, partial femur" A titanosaur[6][14]
File:Pellegrinisaurus Skeleton reconstruction.jpg
Rocasaurus R. muniozi Lower "Partial postcranial skeleton" A titanosaur[6][15]

Theropods

Genus Species Location Stratigraphic position Material Notes Images
Austroraptor A. cabazai Lower A fragmentary skeleton including parts of the skull, lower jaw, a few neck and torso vertebrae, some ribs, a humerus, and assorted bones from both legs A dromaeosaurid
File:Austroraptor Reconstruction.jpg
Bonapartenykus B. ultimus Upper A holotype consists of a mid-dorsal vertebra, both scapulocoracoids, left tibia and femur, left pubis articulated with the pubic peduncle of the ilium, the anterior blade of the left ilium, and two partially preserved eggs. An alvarezsauroid
File:Bonapartenykus (life restoration).png
Lamarqueavis L. australis Lower "Right coracoid with damaged sternal and omal extremities, and lacking acrocoracoidal process" An ornithuran[16]
Limenavis L. patagonica Lower "Partial forelimb" An ornithuran[6][17]
Niebla N. antiqua Upper Braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs, and incomplete vertebrae. An abelisaurid[18]
File:Abelisauridae-Niebla-antiqua.jpg
Quilmesaurus Q. curriei Upper Femur and distal tibia An abelisaurid[6][19]
File:Quilmesaurus curriei.jpg

Pterosaurs

Fragmentary fossils are known from the formation.[6]

Genus Species Location Stratigraphic position Material Notes Images
Aerotitan A. sudamericanus Bajo de Arriagada Upper Partial rostrum The first unambiguous azhdarchid from South-America[20]
File:Aerotitan sudamericanus.png

Fish

Genus[3] Species Location Stratigraphic position Material Notes Images
Atlantoceratodus A. patagonicus 3 tooth plates A ceratorontiform lungfish[21]
Belonostomus B. lamarquensis A aspidorhynchid fish[22]
Chondrichthyes indeterminate 11 vertebral centra
Diplomystidae indeterminate 4 incomplete pectoral spines
Siluriformes indeterminate 5 incomplete pectoral spines
Lepisosteidae indeterminate 6 vertebral centra
Teleostei indeterminate 10 isolated teeth
cf. Percichthyidae indeterminate 19 fragmentary vertebrae

Squamata

Genus[3][23] Species Location Stratigraphic position Material Notes Images
Patagoniophis P. parvus incomplete trunk vertebra
Alamitophis A. argentinus incomplete trunk vertebra
Madtsoiidae indeterminate incomplete trunk vertebra
?Scincoidea indeterminate incomplete left maxilla
Pleurodonta indeterminate incomplete left maxilla
Teiioidea indeterminate incomplete right maxilla

Turtles

Genus Species Location Stratigraphic position Material Notes Images
Iaremys I. batrachomorpha A chelid turtle[24]
Trapalcochelys T. sulcata A meiolaniform turtle[25]
Yaminuechelys Y. gasperinii A chelid turtle

Rhynchocephalia

Genus Species Location Stratigraphic position Material Notes Images
Lamarquesaurus L. cabazai Cerro Tortuga [26]

Plesiosauria

Genus Species Location Stratigraphic position Material Notes Images
Kawanectes K. lafquenianum Quarry of the “Bentonitas Patagónicas” company Upper A partial skeleton consists of six cervical vertebrae, three dorsal vertebrae, three sacral vertebrae, nine caudal vertebrae, right femur, right humerus, ilium, one 216 mesopodial element, one caudal phalanx and one caudal rib . An elasmosaur.
File:Kawanectes lafquenianum.png

Frogs

Unnamed frogs belonging to the family Calyptocephalellidae and Leptodactylidae, and those with no family designation were also found.[27][3]

Genus Species Location Stratigraphic position Material Notes Images
Calyptocephalella C. satan Calyptocephalellid frog[28]
Kuruleufenia K. xenopoides Pipid frog[29]

Mammals

The mammal fauna of the Allen Formation is known from seven teeth, which document the presence of several species.[30]

Genus Species Location Material Notes Images
Mesungulatum M. lamarquensis Cerro Tortuga Two upper molars and a fragmentary lower molar A dryolestoid
Groebertherium G. stipanicici Cerro Tortuga One upper molar A dryolestoid
cf. Brandonia sp. Cerro Tortuga One lower molar A dryolestoid
Barberenia B. allenensis Cerro Tortuga One upper molariform A dryolestoid
Solanutheirum S. walshi Cerro Tortuga A right lower molar and left dentary fragment. A meridiolestid.[31]
Trapalcotherium T. matuastensis Cerro Tortuga One first lower molar A gondwanathere

Plants

Genus Species Location Stratigraphic position Material Notes Images
Podocarpoxylon P. mazzonii Valcheta Petrified Forest, Río Negro Province.[32] Fossil wood[32]

See also

References

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  1. ↑ Salgado et al., 2007
  2. ↑ Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, South America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 600-604. Template:ISBN.
  3. ↑ a b c d Martinelli, A. and Forasiepi, A.M. (2004). "Late Cretaceous vertebrates from Bajo de Santa Rosa (Allen Formation), Rio Negro province, Argentina, with the description of a new sauropod dinosaur (Titanosauridae)". Revista del Museo Argentino de Ciencias Naturales 6(2): 257–305.
  4. ↑ a b Armas & Sánchez, 2015, p.101
  5. ↑ Armas & Sánchez, 2015, p.110
  6. ↑ a b c d e f g h Weishampel et al., 2004, p.604
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Coria et al., 2012
  11. ↑ Juárez Valieri et al., 2010
  12. ↑ a b "63.10 Provincia de Río Negro, Argentina; 4. Río Colorado Formation," in Weishampel, et al. (2004). Page 604.
  13. ↑ Rolando et al., 2022
  14. ↑ a b "Table 13.1," in Weishampel, et al., 2004, p.269
  15. ↑ "Table 13.1," in Weishampel, et al., 2004, p.270
  16. ↑ Agnolin, 2010
  17. ↑ "Table 11.1," in Weishampel, et al., 2004, p.215
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ "Table 4.1," in Weishampel, et al., 2004, p.77
  20. ↑ Novas et al., 2012
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ Script error: No such module "Citation/CS1".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ Script error: No such module "Citation/CS1".
  25. ↑ Script error: No such module "Citation/CS1".
  26. ↑ Apesteguía & Rougier, 2007, p.3
  27. ↑ Script error: No such module "Citation/CS1".
  28. ↑ Script error: No such module "Citation/CS1".
  29. ↑ Script error: No such module "Citation/CS1".
  30. ↑ Rougier et al., 2009
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ a b Script error: No such module "Citation/CS1".

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Bibliography

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Further reading

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